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Background: Repeated cross-sectional serosurveys in the same geographic area establish the trend of the evolving pandemic. We present the findings of the third round of a national serosurvey to estimate the seroprevalence of SARS-CoV-2 infection among the general population and health care workers of India. Methods: We conducted the third population-based serosurvey between Dec 18, 2020 and Jan 6, 2021 in the same 700 villages or wards from 70 districts in 21 states across India, which were selected for the first and second serosurveys. We enrolled from each district, at least 400 individuals aged ≥ 10 years from general population and 100 HCWs from sub-district level public health facilities. Serum samples from general population were tested for the presence of IgG antibodies against nucleocapsid (N) and spike protein (S1-RBD) of SARS-CoV-2 using the Abbott and Siemens assays respectively, whereas sera from HCWs were tested for anti-S1-RBD. For general population, sera positive for either of the antibodies were considered positive, while sera positive for anti-S1-RBD were considered as positive for HCW. Weighted seroprevalence estimates were adjusted for sensitivity and specificity of respective assays. Findings: Of the 28,598 sera from general population, 4585 (16%) had IgG antibodies against N, 6647 (23.2%) against S1-RBD and 7436 (26%) against either. The weighted and assay characteristic adjusted seroprevalence against either of the antibodies was 24.1 (95%CI: 23.0% to 25.3%). Seroprevalence was lower in rural areas (21.4%, 95% CI: 20.3% to 22.6%) compared to urban non-slum (29.4%, 95% CI: 26.9% - 32.1%) and slum areas (34.6%, 95% CI: 31.0% to 38.3%). Among 7385 HCWs, the seroprevalence of anti-S1-RBD IgG antibodies was 25.6% (95% CI: 23.5% to 27.8%). Interpretation: Nearly one in four individuals aged 10 years or older from general population as well as HCWs were exposed to SARS-CoV-2 by December 2020 amounting to 271 million infections in India. Funding Statement: Indian Council of Medical Research Declaration of Interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf and declare no competing interests Ethics Approval Statement: The project was approved by Institutional Human Ethics Committee at ICMR-National Institute of Epidemiology.

Background: ChAdOx1 nCoV-19 Corona Virus Vaccine (Recombinant) (SII-ChAdOx1 nCoV-19), manufactured in India at Serum Institute of India Pvt Ltd (SIIPL) after technology transfer from AstraZeneca, was evaluated in this phase 2/3 immunobridging study. Methods: This observer-blind study randomised participants 3:1 to SII-ChAdOx1 nCoV-19 or AZD1222 (ChAdOx1 nCoV-19) (immunogenicity/reactogenicity cohort) and 3:1 to SII-ChAdOx1 nCoV-19 or placebo (safety cohort). Two doses of vaccine (5 × 10¹⁰ viral particles) or placebo were given at 4-week intervals (+2-week window). Primary objectives were to demonstrate non-inferiority of SII-ChAdOx1 nCoV-19 to AZD1222 in terms of geometric mean titre (GMT) ratio of anti-SARS-CoV-2 spike immunoglobulin G (IgG) antibodies 28 days after second dose (defined as lower 95% CI >0·67) and to determine the incidence of serious adverse events (SAEs) causally related to SII-ChAdOx1 nCoV-19. Anti-spike IgG response was assessed using a validated multiplexed electrochemiluminescence-based immunoassay. Safety follow-up continued until 6 months after first dose. Findings: Between August 25 and October 31, 2020, n=1601 participants were enrolled: n=401 to the immunogenicity/reactogenicity cohort and n=1200 to the safety cohort. After two doses of SII-ChAdOx1 nCoV-19 or AZD1222, seroconversion rates for anti-spike IgG antibodies were 98·0% and 98·9%, respectively, with anti-spike IgG GMTs of 30 245·6 AU/mL (95% CI 26 794·0–34 141·8) and 28 558·3 AU/mL (23 479·3–34 735·8); SII-ChAdOx1 nCoV-19 was non-inferior to AZD1222 (GMT ratio 0·98; 95% CI 0·79–1·23). SAEs were reported in 15/1200 (1·3%, 95% CI 0·7–2·1), 2/300 (0·7%, 0·1–2·4) and 2/100 (2·0%, 0·2–7·0) participants who received SII-ChAdOx1 nCoV-19, placebo and AZD1222, respectively; none were causally related. SARS-CoV-2 infections were observed in 1·9% (n=22), 3·4% (n=10) and 2·0% (n=2) of the SII-ChAdOx1 nCoV-19, placebo and AZD1222 groups, respectively; none were severe. Interpretation: SII-ChAdOx1 nCoV-19 has a non-inferior immune response compared to AZD1222 and an acceptable safety/reactogenicity profile. Trial Registration: This study was registered with number CTRI/2020/08/027170 Funding: SIIPL, Indian Council of Medical Research, AstraZeneca. Declaration of Interest: PSK, CB, AD, MG, US, DK, and BG are employees of SIIPL. JV and EJK are employees of AstraZeneca. All other authors declare no competing interests. Ethical Approval: The study was approved by the Drugs Controller General of India (DCGI) and the ethics committees of each study site.

Background: India witnessed a severe second wave of COVID-19 during March and June 2021. We did the fourth nationwide serosurvey to estimate prevalence of SARS-CoV-2 antibodies in the general population aged >=6 years and health care workers (HCWs). Methods: We did a cross-sectional study between 14 June and 6 July 2021 in 700 clusters in the same 70 districts across 21 states/Union Territory. From each district, a minimum of 400 individuals aged >=6 years from general population and 100 HCWs from the district public health facilities were included. The serum samples were tested for the presence of IgG antibodies against S1-RBD and nucleocapsid protein of SARS-CoV-2 using chemiluminescence immunoassay. We estimated the weighted and test adjusted seroprevalence of IgG antibodies against S1-RBD and/or nucleocapsid protein along with 95% CI. Findings: Of the 28,975 sera tested, the weighted and test adjusted prevalence of IgG antibodies against S1-RBD and/or nucleocapsid protein among the general population aged >=6 years was 67.6% (95% CI: 66.4 – 68.7). The seroprevalence increased with age and was not different in rural and urban areas. Compared to unvaccinated adults (62.3%, 95% CI: 60.9 – 63.7), seroprevalence was significantly higher among individuals who received one (81.0%, 95% CI: 79.6 - 82.3) and two doses (89.8%, 95% CI: 88.4 - 91.1). The seroprevalence of IgG antibodies among 7,252 health care workers was 85.2% (95% CI: 83.5 - 86.7). Interpretation: Nearly one third of the population is still seronegative. It is necessary to accelerate the coverage of COVID-19 vaccination among adults and continue adherence to non-pharmaceutical interventions. Funding: Indian Council of Medical Research. Declaration of Interest: None to declare. Ethical Approval: The Institutional Human Ethics Committee of the ICMR National Institute of Epidemiology, Chennai approved the study protocol.

Background: The incidence, manifestations, outcome and clinical predictors of paradoxical TB-IRIS in patients with HIV and culture confirmed pulmonary tuberculosis (PTB) in India have not been studied prospectively. Methods: HIV+ patients with culture confirmed PTB started on anti-tuberculosis therapy (ATT) were followed prospectively after anti-retroviral therapy (ART) initiation. Established criteria for IRIS diagnosis were used including decline in plasma HIV RNA at IRIS event. Pre-ART plasma levels of interleukin (IL)-6 and C-reactive protein (CRP) were measured. Univariate and multivariate logistic regression models were used to evaluate associations between baseline variables and IRIS. Results: Of 57 patients enrolled, 48 had complete follow up data. Median ATT-ART interval was 28 days (interquartile range, IQR 14–47). IRIS events occurred in 26 patients (54.2%) at a median of 11 days (IQR: 7–16) after ART initiation. Corticosteroids were required for treatment of most IRIS events that resolved within a median of 13 days (IQR: 9–23). Two patients died due to CNS TB-IRIS. Lower CD4 + T-cell counts, higher plasma HIV RNA levels, lower CD4/CD8 ratio, lower hemoglobin, shorter ATT to ART interval, extra-pulmonary or miliary TB and higher plasma IL-6 and CRP levels at baseline were associated with paradoxical TB-IRIS in the univariate analysis. Shorter ATT to ART interval, lower hemoglobin and higher IL-6 and CRP levels remained significant in the multivariate analysis. Conclusion: Paradoxical TB–IRIS frequently complicates HIV-TB therapy in India. IL-6 and CRP may assist in predicting IRIS events and serve as potential targets for immune interventions.